It is very easy to do a conversion yourself - you just need someone to fabricate 2 brackets for you (if you can't do it). The parts you need are:
2x RRC hubs or 110 front hubs (early 110 not post '93 D110) - they narrowed the wheel bearing spacing on disco's defenders and RRC's after about '92-'93.
2x disc calipers - either RRC front, or any locally available ones like willwood (as long as they are at least 2-piston and about the right size - RRC rears are too small for a 110).
2x 110 or RRC FRONT discs
1x adjustable brake proportioning valve (willwood, volvo, etc).
2x brackets (these need to be fabricated) with longer grade 8 spindle-housing flange bolts - an off the shelf D60 bracket may be able to be adapted.
The rest is pretty self-explanatory. The brakes may not be a heap better than the drums, but they are easier to work on.